The user subroutine ``ucreep.f'' is made available to allow the user to incorporate his own creep law by selecting the keyword sequence *CREEP,LAW=USER in the input deck. The creep law gives the Von Mises stress as a function of the equivalent creep strain rate. The header and a description of the input and output variables is as follows:
subroutine ucreep(amat,iel,iint,t1l,epini,ep,dtime,svm,dsvm)
!
! INPUT:
!
! amat: material name
! iel: element number
! iint: integration point number
! t1l: temperature
! epini: equivalent creep strain at the start
! of the increment
! ep: present equivalent creep strain
! dtime: time increment
!
! OUTPUT:
!
! svm: present Von Mises stress
! dsvm: derivative of the Von Mises true stress with respect
! to the present equivalent creep strain.
! Numerically: change the present equivalent
! strain with a small amount, calculate the amount
! of change this causes in the present Von Mises
! true stress, and divide the latter amount through the
! former amount.